Osteoporosis affects 25 million women and men in the United States and resulted in 500,000 vertebral crush fractures, more than 250,000 hip fractures, and 200,000 distal radius fractures annually. An effective way of treating and preventing osteoporosis involves employing antiresorptive agents such as estrogen, calcitonin, and bisphosphonates. These agents suffer, however, from limited efficacy or undesired side effects. For example, estrogen therapy, which leads to an increase bone density at the lumbar spine in women, also brings about undesirable side effects such as weight gain and breast tenderness. In addition, concerns of a higher risk of breast and endometrial cancer that associates with long term estrogen treatment has prompted researchers to search for other agents that carry less side effects.
Chinese discovered centuries ago that plants of the genus Epimedium can strengthen bone and connective tissues. The general effect has been attributed to flavones (e.g., icariin, epimedins, anhydroicaritin, and karmferol), a class of compounds that are found in extracts of Epimedium plants.